Air quality meter

ABSTRACT

A portable air quality monitoring device is disclosed that can identify the type of particles in the air. This device takes images of particles in the air and compares them with a library of particles in its memory to identify the type of particles. The device has a housing that draws ambient air into the system and takes microscopic images of the flowing particles and droplets using flash photography. The device can be stand alone or can connect to the back of a mobile phone and use the mobile phone camera and light. People can upload their local air quality data online for all to see the local air quality.

FIELD OF THE INVENTION

The present invention relates, in general, to air quality monitoringsystems, and in particular, to an imaging-based particle recognitionsystem.

BACKGROUND OF THE INVENTION

Air quality is one of the most important factors affecting health,productivity, and learning ability. Air quality can significantly affectpeople with chronic lung conditions, like asthma and COPD. Pollens andother particles can trigger their symptoms. In addition, viruses (suchas Corona virus) are known to transmit through droplets that aregenerated by an infected person, when talking or coughing. Thesedroplets are mainly spherical and have diameters of larger than 5 μm.

A handheld device that can check if there are significant amounts ofparticles and droplets in the air would indicate the air quality. Airquality monitoring is performed by a variety of instruments, dependingon what is being measured. To measure hazardous gases and chemical, gasanalyzers are used. The air samples are sent to a laboratory that isequipped with gas analyzing machines to identify the gases and chemicalsin the air. Because the gas analyzing machines are large and quiteexpensive, this test is not performed on location. Similarly, if themorphology of the particles in the air are needed, the air sample issent to a laboratory that is equipped with particle morphology equipmentto identify the particle. Particle morphology devices use imaging toidentify the particle.

Portable air quality monitoring devices mainly count the number ofparticles in the flow. If the number of particles is large, the airquality is noted as poor, otherwise it is good. These handheld devicescan immediately provide particle counts in the air. These devices workby using a laser to count the number of particles in the air, or byusing electrochemical sensors to detect gaseous compounds. A particlecounter operates by pumping an air sample past a laser beam. A particlein the air scatters the laser light. A photodetector senses thescattered light and generates an analog electrical signal. The signalsare analyzed to determine the particle size and count.

None of the currently available handheld air quality monitoring devicescan distinguish the type of the particles in the air, they only measurethe number, the sizes, and the chemical composition the particles. Inaddition, the currently available air quality measurement devices cannotdifferentiate liquid droplets from other particles. There is no existingsolution for the general public to attain the quantity of droplets inambient air. The present device uses direct imaging and an imagerecognition software to identify the particles. It can identify theparticles in the air by comparing them with a library of particles inits memory. It has a user interface to interpret environmental data andtell the user if the environment is safe or not.

The present device is designed to determine the type of the particles,if it is a solid or a liquid, and if it is a solid, what type ofparticle it is. The present device is aimed at detecting potential forair born particles and water droplets as a catalyst for virustransmission, and thereby prevent asthma attacks and reduce diseasetransmission through warning people of unsafe environments.

SUMMARY OF THE INVENTION

A new handheld device is disclosed that not only provides the airquality information regarding the number of particles in the air, butalso it identifies the types of particles in the air. It can distinguisha liquid droplet from a solid particle, a dust from a pollen, asynthetic fiber from a metal particle, etc. This device uses a fastimage processing system that is trained to rapidly recognize a set ofpredefined particles. An application software is also developed to showall the measured and analyzed data on the user's phone for easy access.This portable device can measure the size and number of the droplets andparticles in an air space. The number of particles/droplets in the airis used as an indicator of the air quality. The device comprises of afan that takes in an ambient air into the device. The air passes througha narrow channel inside the device while microscopic images are taken.The images are processed by an image processing system and are comparedwith a library of images in the device to identify the type ofparticles. The image processing also counts the number of the particlesand determines their sizes.

The present device provides particle morphology. The device has anautomated image analysis system and trains to identify specificparticles. Machine learning technology has allowed the image processingand image recognition process to be done in a fraction of a second. Thisallows the system to immediately identify the particle and report to theuser. The device can be paired with a mobile phone, and uses its GPSsystem to show the air quality throughout all geographical locations andplaces of interest to people.

The device can also identify if the particles are water droplets orsolid particles. The higher the number of airborne droplets, the higherthe chances of inhaling infectious particles. In one embodiment of thepresent invention, the device pairs with a mobile phone and all the dataare shown on an App that is installed on the phone. In anotherembodiment of the present invention, the device has its own monitor andcan be used as an independent device. In another embodiment of thepresent invention, the device can attach to the back of a mobile phoneand use its camera and light. One objective of the present invention isto sample ambient air and measure the quantity of liquid droplets.Another objective of the present invention is to have a device such thatthe readings should be instantaneously visible to the user so they canmonitor environments in real-time. Another objective of the presentdevice is to provide a portable device for use anywhere. To performthese functions, the device samples ambient air and analyzes samples toquantify the droplets within. The device can be connected to asmartphone or have its own display to present results. It is alsoconfigured to be inexpensive since the client intends to commercializethe device. Another object of the present invention is to allow peopleknow if the air quality in a place is hazardous before they enter theplace. When entering a room, getting on a bus or a car, going shoppingin a store or a mall, the present device will inform if there is anypotentially hazardous particles or droplets. Another objective of thepresent device is provide a device that people can share the air qualityinformation with others. By immediately uploading the local air qualityinformation online, others can see the air quality in the places oftheir interest.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments herein will hereinafter be described in conjunction with theappended drawings provided to illustrate and not to limit the scope ofthe claims, wherein like designations denote like elements, and inwhich:

FIG. 1 shows the first embodiment of the present invention;

FIG. 2A shows a perspective of the second embodiment of the presentinvention with its top cap removed;

FIG. 2B shows a perspective of the second embodiment of the presentinvention;

FIG. 3 shows a third embodiment of the present invention;

FIG. 4 shows another embodiment of the present invention that attachesto a mobile phone;

FIG. 5 shows a sample of images of droplets and edge recognition processof the image processing system of the present invention;

FIG. 6 shows a sample of images of particle in the library of the imagesin the present invention,

FIG. 7 shows a sample of the images of the particles taken by theimaging system.

DETAILED DESCRIPTION

FIG. 1 shows the first embodiment of the present invention. The device10 comprises of a substantially rectangular housing 11 that isconfigured to contain an air receiving channel 12, a microscopic imagingsystem 14, a lighting system 16 that can generate a short durationflash, a fan 18 that draws the air 1 into the system, a processor tocontrol the operation of the system and a power supply. The housing alsocomprises of slots so that the tactile switch and the charging port forthe power supply are easily accessible from the outside of the device.

Air 1 is taken into the device 10 through the intake channel 12. The fan18 draws the air into the system. The air is guided through a channelfor microscopic observation. The device is configured to be handheld orattach to the back of a mobile phone. It can have a power grip betweenthe palm and thumb of the user's hand, while small enough to beconsidered portable, the housing is also long enough to fit within theoptimum range for a power grip surface. The height, length and width ofthe device are all within the optimum range for handheld devices and itconforms to other ergonomic standards by having rounded edges andallowing a grip with all fingers on the hand. In one embodiment thedevice is 8 cm×16 cm×0.5 cm.

The microscopic imaging system 14 comprises of a miniature camera 22,such as a charge coupled device (CCD) or a Raspberry Pi Zero W, and acamera controller and processor 24 that is wired 25 to the camera 22.The controller is configured to allow for fast image processing. Thecamera has a Bluetooth and Wi-Fi connectivity built-in, allowing thedevice to operate wirelessly, which enhances its portability andpracticality. This also allows the device to be compatible with multiplemobile device types, and removes the need for an additional cable porton the device, which allows for a smaller form factor. It is importantto have high resolution camera, such as an 8 MP resolution, to be ableto resolve small size drops and particles. The casing is configured tohold the camera in place with a lens 26 focusing onto the flow channel27. The microscopic imaging may comprise an extension tube 28 thatconnect the camera 22 to the lens 26. The lens 26 is a biconvex lenssuch a small spherical glass bead, preferably a 1 mm high-quality glassbead, or a plano-convex lens. The microscope glass bead is placed infront of the camera module to achieve the required magnification. The 1mm glass bead can achieve magnification of up to 350× if placed right onthe lens and can provide more than 2000× if it is placed at the end ofan extension tube away from the camera lens embodiment of the presentdevice. In one embodiment of the present device the extension tube hasfixed length, and in another embodiment of the present device, thedevice is configured to change the length of the extension tube andtherefore, the location of the glass bead and therefore change themagnification. Use of the bead also allows the device to be affordableas they are very low cost. The camera is configured to have a specificfield of view and a specific depth-of-field.

The lighting system 16 comprises of a light source 32 and a lightingcontroller 34. The light source is preferably a light emitting diode(LED) source, but it can be other sources such a laser light. Thelighting system may also comprise of a coated mirror 33 that can reflectsome of the light onto the imaging region for front lighting. The mirroris coated to only provide sufficient light onto the particles and usereflected light to illuminate the front of the particle for bettermorphology identification. The controller of the light source cangenerate very fast flashes of light (short duration flash). The shortflashes are needed to capture focused images of a moving particles. Afraction of a microsecond duration flash of light is used in the orderto freeze the motion of any particles in the flow. If the flash durationis long, a moving article will show as a streak in the images.Preferably an LED Chip and a MOSFET can be used to provide the requiredlighting to illuminate and freeze the motion of the droplets. Ahigh-power LED Chip consumes fairly low power and provides sufficientbrightness with cool white light. The MOSFET provides a higher voltage,which allows the brightness of the LED to increase.

A power source is included inside the device (not shown). Any powersource, such as a UPS-Lite battery pack, can be used. A 1000 mAh polymerlithium battery is generally enough to power the system. These batterypacks can be re-charged.

The fan 18 is used to draw in the ambient air into the system. A smallfan, such as a 10 mm×10 mm×3 mm fan is suitable for this purpose. Anaxial fan can also be used to draw air from one side and eject for theother side, or a tangential inlet fan can be used to intake airtangentially and eject axially.

The flow channel 12 comprises of a focusing section 42 with a narrowflow diameter, about a 2 mm diameter section, that is configured toconcentrate the flow of the air sample within the focusing zone 27 (thefield of view and depth of field) of the camera. It is also designed toallow the air to flow through the channel at a speed which can be imagedwithout blur. The channel is transparent or has a first slot 44 for thecamera to image its contents and a second slot 45 opposite for the lightso that the channel can be illuminated and the motion of thedroplets/particle is frozen.

FIGS. 2A-B show perspectives of another embodiment of the presentdevice. The inlet 201 is set on one side of the device, with an outletgrid 202 on the front face of the device. The camera 206 and the lightsource 208 are set to image the flow inside the channel 210. FIG. 2Bshows the set of tactile switches 212 and an ON/OFF switch 214 are usedto control the device.

The tactile switches 212 is used to toggle the camera between itsstandby and active state. The tactile switch is placed at the outside ofthe housing so it is accessible for the end user. The power switch 214puts the camera into a standby state in which it consumes minimal power,helping maintain the battery life of the device.

In the first embodiment of the present device shown in FIG. 1, the lightsource is located on the opposite side of the camera for backlightingand a coated mirror on the front side for reflection and front lighting.In the second embodiment of the present device shown in FIG. 3, thelight source 306 is located on the same side of the camera 302. A lightguide 308 is located on the opposite side of the camera 302. The lightguide receives the light from the light source and channels it such thatit directly illuminates the flow channel providing shadow images of theparticles in the flow. This system makes the device more versatile andcompact.

In the third embodiment of the present device, the device configured toremotely connect to a mobile phone and show all the results on anapplication on the mobile phone.

In the fourth embodiment of the present device, the device has its ownmonitor and shows all the results on the monitor (not shown).

In the fifth embodiment of the present device, as shown in FIG. 4, thedevice 401 is configured to attach to the back of a mobile phone 402 anduse the camera 403 and the light source 404 of the mobile phone. Thedevice comprises of a magnifying lens 411 that is configured to beplaced in front of the camera of the phone 403. The device has a lightguide 412 to receive the light from the phone flash and reflect it backtowards the channel 414 and into the camera. Thereby taking shadowimages of the particles that flow inside the channel. The fan 420 drawsthe air into the channel 414. The device may use the mobile processorand an app to do all its operation or have its own processor 430. It mayalso use the phone battery source or have its own battery source 440.

A set of images are taken, and the size and number of droplets aremeasured. The results are presented as a simple air quality depending onthe number and size of droplets in the air. The air quality is groupedas best, better, good, average, bad, and worse based on the number ofdroplets in the air. The categories are relative to the average count ofdroplets in the environment. The results are shown as TotalParticle/Droplet Count, which displays the total number of particles anddroplets detected in the analysis, the distribution of different typesof particles detected and sorted by count and size.

The processor comprises of an image processing software, a controlsoftware, and a Bluetooth-enabled mobile application. The imageprocessing software can identify particles. The main processes that areachieved by the image processing software, comprise of the following: Asshown in FIG. 5, the images are converted to grayscale 501; the edges502 of the image are found; the edges are closed using dilation followedby erosion, where dilation means that the pixels around the edges arebrightened, essentially expanding the edge, and erosion means that theboundaries of the edges are removed which mostly undoes the previousdilation step (this process expands to fill in any gaps around theperimeter of the droplet, making it one whole edge); findContoursfunction to find the contours in the image which are curves followingthe previously found edges which form closed shapes; the perimeters andareas of the contours are found, and using a circularity formula,circular contours are obtained; these circular contours are chosen iftheir areas are above a threshold value; the contours are used to countthe number of droplets and obtain their respective areas, and the totalnumber of droplets and all the gathered areas is returned, and finally,each image is compared with a set of images in the system data based toidentify the particular particle.

The present device provides particle morphology. The device has anautomated image analysis system and is trained to identify specificparticles. Machine learning technology has allowed the image processingand image recognition process to be done in a fraction of a second. Thisallows the system to immediately identify the particle and report to theuser. Image recognition uses machine learning based algorithm to rapidlyidentify the particle. The system has a library of images for differentparticles of interest. FIG. 6 shows some examples of the pollen imagesin the library of the images: pine (Pinus), mulberry (Morus), birch(Betula), alder (Alnus), cedar (Cedrus), hazel (Corylus), hornbeam(Carpinus), horse chestnut (Aesculus), willow (Salix), poplar (Populus),plane (Platanus), linden/lime (Tilia), and olive (Olea), ryegrass(Lolium sp.) and timothy (Phleum pratense), ragweed (Ambrosia), plantain(Plantago), nettle/parietaria (Urticaceae), mugwort (ArtemisiaVulgaris), Fat hen (Chenopodium), and sorrel/dock (Rumex).

The image processing identifies the edges of the digital image of theparticle by dark pixels. A number of different image processing softwarecan be used, including, Image J, Metamorph, Image Pro Plus, NIH Imageand the like.

The device can be paired with a mobile phone, and uses its GPS system toshow the air quality throughout all geographical locations and places ofinterest to people.

A method is used to identify a liquid droplet from a solid particle.Liquid droplets are spherical since the surface tension of the liquidforces a liquid droplet to become spherical. Therefore, a liquid dropletcan be distinguished from a solid particle based on its sphericity,which translate to circularity in a two dimensional image. The shapecircularity is defined as 4π×area/(square of perimeter). The closer thisparameter is to 1, the closer the shape is to being a circle. Throughexperimental validation, a value of at least 0.85 for the circularitywas determined to be a good indicator of a droplet.

A mobile application serves as the primary interaction between ourdevice and other devices. The application sends data packets between theapplication and the camera with minimal energy consumption. In thisapplication, the user can connect their phone to the device, initiate atest, and view the results.

The application consists of a Home Screen and Results Screen, and isdesigned to minimize the number of user interactions needed to garner aresult. Overall, operating the device and beginning a test only takestwo interactions. The app is configured to provide the results to a userin a simple and intuitive manner. The user will open the app and startthe measurement.

The system further comprises of an artificial intelligent (AI) system torapidly identify the morphology of the particles. The method is asprovided in U.S. Pat. No. 7,218,775, which is incorporated by referencein the present system.

The device also has a network architecture that is capable ofautomatically collecting environment data and transferring them to adatabase. Our monitoring device paired with a mobile network systemmeasures local air quality and share that data with the mobile networkfor others to know the information. The network architecture is capableof automatically collecting environment data and transferring them to adatabase. The monitoring device paired with a mobile network systemmeasures local air quality and share that data with the mobile networkfor others to know the information. The use of air quality sensornetworks is an important solution to assure the monitoring of thelocations of high concentration of large droplets and potential zonesfor virus transmission. The acquired data is transmitted to a mobilecomputing unit expressed by a smart phone.

The present air monitoring system can also recognize metal and metaloxide particles that are generated by combustion or burning of oil indifferent types of engines. In most reciprocating piston engines, thecleanness of the oil is essential for the proper operation and life ofthe engine. One of the causes of the oil deterioration are the metalparticles in the oil. As the oil circulates in the system, metalparticles from various sources in the flow system may enter the flow.The current process is to sample the oil and send it to a laboratory todetermine the particles content. The present monitor can be used tosample the exhaust gases from the engine and determine the number andconcentration of the metal or metal oxide particles. These areindicators of the amount of the particles in the oil.

In another embodiment of the present system, an ionizer is coupled withthe system to filter the air. If the air monitoring system identifiedharmful particles, the system turns ON and the ionizer to filter theair. An ionizer charges particles which are then attracted by a surfaceby electrostatic forces.

In another embodiment of the present system, a light scattering systemis added in order to be able to measure submicron sizes particles. Thelight scattering system is similar to the U.S. Pat. No. 8,958,067 whichis incorporated by reference.

In another embodiment of the present system, the device furthercomprises of a sensor to identify the biochemical characteristics of adroplet, differentiating potentially disease ridden droplets from othermoisture droplets in the air.

The invention claimed is:
 1. A portable air quality monitoring system,comprising: a) a housing configured to have an air inlet port, an airoutlet port, and a channel configured to guide an ambient air flowthrough the device; b) a fan placed inside the housing to draw theambient air flow into the device; c) a microscopic imaging system placedinside the housing and is configured to take images of the ambient airflow that contains a set of particles; d) a lighting system placedinside the housing and is configured to generate a short duration flashof at least 1 microsecond duration in synchronization with themicroscopic imaging system to take images of the set of particles insidethe ambient air flow of the channel, wherein the lighting systemcomprises of a light source placed on an opposite side of themicroscopic imaging system for backlighting and a coated mirror placedon the same side of the microscopic imaging system for front lighting,with respect to the channel, e) a processor having an image processingsoftware configured to i) identify a solid particle from a water dropletby determining a circularity of a particle image, wherein thecircularity is defined as 4π times an area of the particle image overthe square of a perimeter of the particle image and wherein a particleis identified as the water droplet if the circularity is more than 0.85,ii) identify a morphology of the particle by comparing the particleimage with a set of predefined particle images stored in a memory of thedevice, iii) identify a size and a number of the set of particles, iv)report a set of air quality data, wherein the set of air quality datacomprise of the morphology and a size distribution and the number of theset of particles, and f) a power supply and a set of tactile switches tocontrol an operation of the device.
 2. A portable air quality monitoringsystem, comprising: a) a housing configured to have an air inlet port,an air outlet port, and a channel configured to guide an ambient airflow through the device; b) a fan placed inside the housing to draw theambient air flow into the device; c) a microscopic imaging system placedinside the housing and is configured to take images of the ambient airflow that contains a set of particles; d) a lighting system placedinside the housing and is configured to generate a short duration flashof at least 1 microsecond duration in synchronization with themicroscopic imaging system to take images of the set of particles insidethe ambient air flow of the channel, wherein the lighting systemcomprises of a light source placed on the same side of the microscopicimaging system for front lighting and a lightguide placed on theopposite side of the microscopic imaging system to guide the light forbacklighting, with respect to the channel, e) a processor having animage processing software configured to i) identify a solid particlefrom a water droplet by determining a circularity of a particle image,wherein the circularity is defined as 4π times an area of the particleimage over the square of a perimeter of the particle image and wherein aparticle is identified as the water droplet if the circularity is morethan 0.85, ii) identify a morphology of the particle by comparing theparticle image with a set of predefined particle images stored in amemory of the device, iii) identify a size and a number of the set ofparticles, iv) report a set of air quality data, wherein the set of airquality data comprise of the morphology and a size distribution and thenumber of the set of particles, and f) a power supply and a set oftactile switches to control an operation of the device.
 3. A portableair quality monitoring system, comprising: a) a housing configured toattach to a back of a mobile phone, and has an air inlet port, an airoutlet port, and a channel configured to guide an ambient air flowthrough the device; b) a fan placed inside the housing to draw theambient air flow into the device; c) a microscopic optics configured tobe placed in front of a camera of the mobile phone and is configured totake images of a set of particle in the ambient air flow; d) a lightguide placed inside the housing and in front of a light source of themobile phone to reflect light back onto the channel; e) an applicationinstalled on the mobile phone to control the camera and the light sourceof the mobile phone to generate a short duration flash of at least 1microsecond duration in synchronization with the camera to take imagesof the set of particles inside the ambient air flow of the channel andto i) identify a solid particle from a liquid droplet by determining thecircularity of the particle image, wherein the circularity is defined as4π times the area of the particle image over the square of the perimeterarea of the particle image and wherein the particle is identified as aliquid droplet if the circularity is more than 0.85, ii) identify amorphology of a particle by comparing an image of a particle with a setof predefined images stored in the processor, iii) identify the size andthe number of the set of particles, iv) report a set of air qualitydata, wherein the set of air quality data comprise of a morphology and asize of each particle in the set of particles and a number of theparticles in the ambient air flow.